The invention relates to an indicating device including adjustable rated or limited value markers. Electrical signals are produced when the limit value markers are reached or exceeded. The actual indicating device comprises light emitting diodes, liquid crystals, or gas discharge indicator elements arranged in a row.
Electrical indicator instruments comprising adjustable limit values are known in different types. In the most common form such an indicating instrument comprises a moving coil meter and a scale. The moving coil meter is provided additionally with one or more rated value or limit value pointers which are adjustable from the outside of the instrument. The rated value or limit value pointers are mechanically coupled with sensors which trigger a switching signal as soon as the measured value pointer reaches or exceeds the position of the rated value or limit value pointer. These sensors are, for example, constructed as light barriers, the light barriers of which are either released to pass or interrupted by means of a flag connected to the measured value pointer. In another known construction each of the sensors comprise a coil pair forming part of an oscillator circuit. A flag connected with the measured value pointer interrupts the vibration of the oscillator by reducing the magnetic coupling between the coils.
It is also known to use as an indicating device light emitting diodes arranged in a row instead of a pointer instrument. The indication by means of such a light emitting diode row may be accomplished in analogy to a liquid thermometer in such a manner that the light emitting diodes are all switched on from the beginning of the scale to a certain point along the scale which represents the actually measured value while the remaining light emitting diodes are switched off to the end of the scale. Another known way of indication resides in that only one individual light emitting diode is lit, namely, the one corresponding to the actual measured value while all other light emitting diodes are switched off.